POSIX Shared Memory

shmem_open

In previous chapters, we looked at two techniques that allow unrelated processes to share memory regions in order to perform IPC: System V shared memory (Chapter 48) and shared file mappings (Section 49.4.2). Both of these techniques have potential drawbacks:

• The System V shared memory model, which uses keys and identifiers, is not consistent with the standard UNIX I/O model, which uses filenames and descriptors. This difference means that we require an entirely new set of system calls and commands for working with System V shared memory segments.
• Using a shared file mapping for IPC requires the creation of a disk file, even if we are not interested in having a persistent backing store for the shared region. Aside from the inconvenience of needing to create the file, this technique incurs some file I/O overhead.

  System V shared memory is related to backing store ?

54.5 Comparisons Between Shared Memory APIs

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